Toll-switching system



i-.-. D. M PHERsON TOLL- SWITCHING SYSTEM Filed April 18, 1921 Patented Bliss. 383, 192 i.

HUGH D. MACPHERSON, OF SUMMIT, NE'W JERSEY, ASSIGNOR T0 WESTERN ELECTRIC COMPANY, INCORPORATED, OF NEW YORK, N. Y., A CORPORATION OF NEVI YORK.

TOLL-SWITCHING SYSTEM.

Application filed April 18, 1921.

T 0 all whom it may cancer-n:

Be it known that I, HUGH D. MnolrrnnsoN, a citizen of the United States, residing at- Summit, in the county of Union, State of New Jersey, have invented certain new and useful Improvements in Toll-Switching Systems, of which the following is a full, clear, concise, and exact description.

This invention relates to improvements in switching systems and has particular reference to toll switching systems having means for distributing call wires among outward operators.

An object of the invention is to prevent the connection to a call wire of more than one operators telephone set located at any one of a plurality of operators position during the interval between the operation of any operators calling key and the extension of her set to a preselected call wire.

Another object is to provide novel means whereby the connection to a call wire of more than one operator in any particular group is prevented after the seizure of a call wire by an operator and until said operator restores her calling key.

Other objects will appear in the course of the following description taken in connection with the accompanying drawing which illustrates diagrammatically a preferred embodiment of the inventive idea.

Briefly stated, the invention contemplates dividing a plurality of outgoing operators positions into groups each of which is preferably served by a rotary switch A for con necting any one of the positions of this group to a link circuit B individual to said group. A rotary switch C is also provided which is individual to said link circuit and which is operable to preselect an idle call wire and extend an operators telephone set thereto, the test terminals of all switches C being multipled to prevent the preselection of a busy call wire by another switch.

An allotter mechanism D is provided which is common to the various groups of operators positions and includes a pair of relays individual to each group and to each link circuit. Thus relays 1 and 1 of the allotter are associated with the first group of operators positions and the link circuit B. relays 2 and 2 with the second group of operators positions and another link circuit B, and so on. When an operator in any group attempts to secure a connection to a Serial No. 462,204.

call wire, the two relays of the allotter as signed to said group operate to associate the link circuit individual to the group with the operators telephone set provided that at the time of the initiation of the connection none of the other relays or the remaining pairs are operated or that no other operator in the same group has her calling key actuated. If any of said other relays are energized or the calling key of an operator in the same group with the calling operator is actuated. then the calling operator mustawait the release of said relays or the restoration of said calling key before she can secure connection to a call wire.

It is believed that the invention will now be fully understood from the following detailed description of the operation.

Assuming that the operator in the group served by the switch A whose telephone set is indicated at 6 desires to establish a connection over an idle call wire 7 to an in coming operator at another office, the out ward operator first actuates her calling key 8 whereupon a circuit is established from ground through the lower alternate contact of said key, the conductor 9 which is multipled to the calling keys of all of the operators in the group, the contact and armature of relay 10, the winding of relay 1 and the left hand armatures and contacts of relays 2 to 5 in series togrounded battery. Relay 1 energizes and establishes an obvious operating circuit for relay 1. A connection to ground is then extended through the armatures and front contacts of relays 1 and l, the upper winding of relay 11 of switch C and the contact, armature and winding of the motor magnet 12 of said switch to grounded battery. The motor magnet 12 is marginal and does not operate in series with the upper winding of the relay 11. Brushes of switch G will therefore remain upon the terminals of the idle call wire 7. Relay 11 ene gizes in the circuit through its upper winding and connects ground through its front contact and upper armature to the test brush 13 of switch C whereby a busy potential will be applied to the inultipled test terminals of the switch C through brush 13 to prevent other switches C from seizing the busy call wire. Should any other switch C have its brushes resting upon the terminals of this call wire, the brushes of this switch will he stepped to preselect another idle call wire over a circuit t1 aceable from grounded battery through the winding armature and contact of the motor magnet 12 of said switch, the normal contact and upper armature of relay ll. the brush 1-3 and test terminal, to ground through the brush 1.3 and upper armature and trout contact of relay ll ol the busy switch C. This circuit shunts the upper winding ot' relay 11 and hence the motor magnet 12 oi said other switch will operate. i no idle call wire is Found, the brushes ot the switch will he stepped until brush 13 engages terminal 24 when the switch comes to rest. Then upon the energi zation of the pair of relays of the allotter l) associated with the switch, in response to a call initiated in the associated group of positions. magnet 12- ot the switch will be operated over an obvious ciicuit to step brush 13 from terminal 2% and continue to step said brush until a terminal is encountered upon which there no ground,

The condition of an outward operators position is denoted by ground potential on the terminals over which brush 14. of switch A passes, said ground potential being applied through the normal contacts of the calling key 8 of said idle position. Therefore, upon the operation 01? relay 11 a circuit is extended from grounded battery through the lower armature and front contact of said relay, the winding. armature and contact of motor magnet 15, the inner lower armature and back contact of the relay 16, the brush 14: and the terminal individual to the idle operators position upon which said brush happens to be resting and from thence through the normal contacts of the calling key at said position to ground. The circuit for magnet 15 is self-interrupt ing and said magnet will therefore operate to step the brushes of the switch A until the brush 1% engages the terminal individual to the calling operator at which time ground is no longer encountered and the circuit for motor magnet 15 is permanently opened to cause the brushes of the switch A to come to rest upon the associated terminals indi vidual to the calling operators position. A circuit is immediately established for relay 1G traceable from grounded battery through the lower armature and front contact of relay 11, winding of relay 16, the brush 1'? and the upper alternate cont-act of calling key 8 to ground. Relay l6 energizes to establish a circuit extending from grounded battery througl'i the winding of relay 10, the lowermost armature and front contact of relay 16 and the lower winding of relay 11 to ground. This circuit maintains the relay 11 energized and causes the operation of relay 10 to disconnect the con ductor 9 from the winding of relay 1 which thereuponreleases to open the energizing circuit of. relayl which, after an interval,

also releases. It. will be. apparent that the operation of relay 10 prevents the extension of a circuit from ground through the lower alternate contact of any of the other. calling keys of operators in this group tothe Winding of relay 1 and therefore as long as the calling key S of the calling operator is in its actuated. position after the energization of relay 10, no other operator in the group n'iay secure a connection to an idle call wire. The operation of relay 16 also extends a connection from the operators telephone set (3 through the brushes 1S and 19, the front contacts and two innermost upper armaturcsof relay 16 to the link circuit B and from thence through the brushes 20 and of switch 0 to the call-wire 7. A lamp at the callingoperatofs position is also lighted over a circuit through the brush 2-3 and-the uppermost armature and frontcontact of relay 16 to grounded battery at the lower armature and front contact of relay 11. to indicate to said operator that her telephone set is now connected to a call wire leading to the incoming operator at the distant oflice.

Assuming now thatsubsequent to the operation of the calling key 8 and before the operators set (S'has been connected to the call wire '7; an operator in the second group should initiate a call. The connection to ground at the lower alternate contact otthecalling key of the operator in the second group is extended. through the armature and back contact of a relay similar to relay 1.0, the winding of relay 2 and left armature and contact of relays 3., at. and a in series to grounded battery. Relay 2 will i-uiergize but dueto the energization o l relayl at this time noground willhe connected to the winding'ot relay 2 and this relay will therefore remain. in its normal position. The calling operator in the second group maintains her calling key depressed and awaits the lighting of a lamp:

similarto lamp 22. Then relay 10 oper ates to causethe restoration of relay 1. relay E2 then operates. relay 2 now prevents the closure of a circuit through the winding otrelay 1 so.

that an operator inthe first groupcannot secure a connection vto .a ralli wirewhile. relay 9" is energized.

After rcceivingan assignment of a trunk from the. incoming operator. atthe distant oliicc. the outward operator;v restores her calling key 8.whereuponrelay-lti releases to open the. energizing and holding circuit ror relays 10 and 11.: Theselrelaysthenrelease and the restoration ot the former non .per-

The energiyation. oi

l'lll Lil) iii]

contact of said relay and thereby prevents the operation of motor magnet 15 with the result that the brushes of switch A remain in engagement with the terminals individual to the calling operators position until another call is initiated in the first group whereupon said brushes will be stepped as described to hunt for the terminals individual to a calling position. The release of relay 11 also extinguishes the lam 22.

If it should happen that relays 2 and are energized in response to the initiation of a call in the second group of positions or, in fact, if any of the succeeding groups of relays are energized, a call initiated in the first group must await the release of relays 2 or 3 etc., since the circuit for relay 1 will be opened at the left hand armatures of said relays. In this manner, calls simultaneously awaiting attention in the various groups will be distributed to said groups in the order of their numbers.

What is claimed is:

1. In a switching system, a plurality of groups of operators positions, a plurality of call wires, a link circuit individual to each group of positions, a line finder switch serving each group of positions and operable to connect any one of the positions in the group to said link circuit, and a secand switch individual to said link circuit and operable to preselect an idle call wire whereby an operators position may be extended thereto through said link circuit.

In a switching system, a plurality oi groups of operators positions, a plurality of call wires, a link circuit individual to each group oi positions, a switch serving each group of positions and operable to connect any one of the positions in the group to said link circuit, a second switch individual to said link circuit for joining the same to an idle call wire, and means for preventing the extension of any other operators position in any of said groups to a call wire during the extension of the first named position.

3. In a switching system, a plurality of groups of operators positions, a plurality of call wires, a link circuit individual to each group of positions, a switch serving each group of positions and operable to connect any one of the positions in the group to said link circuit, a second switch individual to said link circuit for joining the same to an idle call wire, and means common to said plurality of groups of po sit-ions for preventing the extension of any other operators position in any of the said groups to a call wire during the extension of the first named position.

a. In a switching system, a group of operators positions, a calling key at each position, a plurality of call Wires, a link circuit for joining any one of said positions to one of said call wires, a switch respon sive to the operation of said calling key for connecting the associated position to said link circuit, and means tor preventing the connection of any other position in the group to a call wire during the interval between the extension of the first named position to a call wire and the restoration oi? said calling key.

In a switching system, a plurality of groups of operators positions, a calling key for each position, a plurality of call wires, link circuits each of which is individual to a group of positions, a switch associated with each oi said link circuits and operable to preselect an idle call wire, a second switch individual to a group of positions and responsive to the operation of a calling key in said group for connecting the associated position to the link circuit individual to said group and the preselected call wire, and means for preventing connection of any other position in said group to a call wire during the interval between the extension of saidassociated position to said preselected call wire and restoration of said calling key.

6. in a switching system, a plurality of operators positions, a plurality of call wires, a link circuit serving said operators positions. a line hunting switch also serving said positions and operable to connect any one of them to said link circuit. and a second switch individual to said link circuit and operable to preselect an idle call wire whereby an operators position may be extended thereto through said link circuit.

7. in a switching system, a plurality of operators positions. a plurality oi call wires to which said positions have access, a link circuit for extending any one of said positions to one of said call wires, and means for preventing the connection of: a second operators position to a call wire while the first named position is being extended.

8. In a switching system, a pin 'ality oi operators positions, a plurality of call wires to which said positions have access. a link circuit for extending any one of said positions to one of said call wires, means for connecting said positions to call wires in a definite sequence when calls are initiated siinultai'ieously at several positions and means at each operators position for indicating when a connection therefrom to the link circuit has been established.

9. In a signaling system, a plurality of groups of operators positions, a plurality of call wires. a link circuit serving each group of positions, means for extending a position in one group over its link circuit to one of said call wires, and means operable when calls are waiting attention in several groups of positions for preventing IOU the extension of a second operators position in said one group before operators positions in the other groups are extended.

10. In a signaling system, a plurality of groups of operators positions, a plurality of call wires, a link circuit serving each group of positions, means responsive to the initiation of a call at one of said positions for extending said positions to a call wire over the link circuit serving the group in which said position is located, and means controlled by the initiation of a call in said group of positions for preventing extension of a second call in said group until a simultaneous call in a difi'erent group of positions has been extended.

11.. In a switching system, a plurality of operators positions, a plurality of call wires, a link circuit serving said operators positions and terminating at one end in movable contacts, fixedcontacts associated with said movable contacts, a circuit extending from each of said operators position to said fixed contacts, means operable when any one of. said operators initiates a call to cause said movable contacts to connect with the fixed contacts associated with said operators position, and a switch at the other end of said link circuit operable to presclect an idle call wire whereby an operators position may be extended thereto through said link circuit.

12. In a switching system, a plurality of operators positions, a plurality of call wires, a switch having a plurality of fixed contact banks and a movable contact for each bank, a key associated with each operators position, circuits for connecting the talking leads to each operators position to certain of said fixed contact banks and for connecting the key at each operators position to other of said fixed contact banks, means operable whenany one of said operators depresses the associated key to cause said movable contacts to connect with the fixed contacts in said banks associated with said operators position, a link circuit connected at one end to said movable contact, and a second switch at the other end of said link circuit operable, to preselect an idle call wire whereby an operators position may be extended thereto through said link circuit.

13. In a switching system, a plurality of operators positions, a plurality of call wires, a switch having a plurality of fixed contact banks and a movable contact for each bank, a key for each operators position, a signal for each operators position, a circuit for connecting each operators position with certain of said fixed contact banks, a circuit for connecting the key of each operators position to other of said fixed contact banks, a circuit for connecting the signal of each operator to another of said fixed contact banks, means operable when any one of said operators depresses her key to cause said movable contacts to connect with the fixed contacts associated with said opera-tors position and operable to actuate the associated signalto indicate to the operator that a connection has been made, a link circuit connected at one end to said movable contacts, and a second switch connected at the other end of said link circuit operable to preselect an idle call wire whereby the operators position connected to the link circuit may be extended to said call wire.

In witness whereof, I hereunto subscribe my name this 15th day of April A. D., 1921.

HUGH D. MAQPHERSON. V 

